T59 Measuring and Modeling Fluxes across the Surface Water/Groundwater Interface II

Sunday, 4 November 2018
1:30 PM - 5:30 PM
Room 132

INFORMATION LOSS IN ELECTRICAL INVERSIONS: NUMERICAL STUDY OF SOLUTE TRACER TESTS IN THE HYPORHEIC ZONE

Paper number: T59-3
Program: Technical Sessions
Time: 1:50 PM – 2:05 PM

Authors

Abstract

Hyporheic zones retain solutes and influence stream water quality, a process that has traditionally been studied with solute tracer injections. Over the last decade, a growing number of injections have been paired with time-lapse resistivity imaging to map the arrival and flushing of solute within the hyporheic zone. Inversion results like pixel breakthrough curves significantly extend our understanding of hyporheic processes but are also influenced by inversion artifacts such as smoothing. Here, we use a synthetic modeling approach to explore questions about the detection capabilities of electrical resistivity imaging for hyporheic zones. For a synthetic channel cross-section, we create a coupled fluid flow, solute transport, and electrical flow model to simulate solute tracer movement and voltage readings during a time-lapse electrical resistivity survey. We then invert the synthetic resistivity data to obtain electrical resistivity images for comparison with known solute distributions. We explore the influence of different solute plateau concentrations, injection periods, and channel geometries. Preliminary results show that inversions detect a significant fraction of salt remaining in the hyporheic zone for several hours after the injection has ended, and the detection window can be extended by increasing the solute concentration of the injection plateau. During the early part of the detection period, the area of the hyporheic zone that contains solute is overestimated due to smoothing in the inversion, but the area rapidly diminishes and becomes underestimated as solute spreads within the hyporheic zone and concentrations decline below detection in the inversion. Our results can be used to guide future field experiments and the interpretation of inversions.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-322606

© Copyright 2018 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.